Fromage is French for cheese.
In Latin 'cheese' was caseus; from this German got käse, Dutch got kaas, Italian cacio, Spanish queso, Portuguese queijo, Irish caise, Welsh caws, and English, of course, got cheese. And then there's the odd one out, French. In France and Belgium they call cheese fromage, which is odd, because the French language gets nearly all of its words from Latin.
And as it turns out, fromage is also a Latin word, it's just the wrong Latin word. Roman legionaries were supplied with a hard cheese called caseus formatus, meaning 'formed cheese' -- that is to say, cheese that was made in a mold. The legionaries eventually shortened this to formaticum, and this then slowly morphed into the modern fromage. This word also entered into the Italian language as formaggio; whether an Italian uses cacio or formaggio depends on the locale, although formaggio appears to be more common.
Fromage is pronounced "frohmazh" (IPA: /frɔ.maʒ/); the plural is fromages. No form of fromage is used in English except in the naming of specific French cheeses (such as fromage frais or fromage de Meaux), or by snotty people who like using French words.